[U-Boot] Fail to flash latest u-boot to firefly-rk3288 emmc

[jExc cHIHAA]

METHOD1. u-boot from rockchip source works, by following steps:
a) git clone: https://github.com/linux-rockchip/u-boot-rockchip.git
b) make
c) ./upgrade_tool UL RK3288UbootLoader_V2.19.01.bin
d) reset board

METHOD2. u-boot-2016.05-rc1 download from u-boot official website doesn't
work:
a) Download source code.
b) make firefly-rk3288_defconfig
c) make

Then I tried with following methods/tools to flash binary file,
unfortunately none works:
i) rkflashtool
Followed instruction in <uboot-src>/doc/README.rockchip, such as:

   ./firefly-rk3288/tools/mkimage -n rk3288 -T rkimage -d \
        ./firefly-rk3288/spl/u-boot-spl-dtb.bin out && \
   cat out | openssl rc4 -K 7c4e0304550509072d2c7b38170d1711 | rkflashtool l

ii) rkflashkit
    ./rkflashkit flash @uboot <binary-file>

iii) upgrade_tool
STEP1: Merge essential header files? Otherwise upgrade_tool refuse to
upgrade.
    ./tools/boot_merger ./tools/rk_tools/RKBOOT/custom-RK3288.ini
STEP2:
    ./upgrade_tool UL <binary-file>


I just want to add ethernet support in u-boot.
Any advice and suggestions will be greatly appreciated.